3D Systems (DDD) grabbed the biggest move among Sector Leaders Thursday -- but not in a way pleasing to its investors. 3D Systems, which has been on a rocky ride in recent weeks, fell 2.86, or 4%, to 62.75 in triple-paced trade. The stock is still 40% above its 44.90 buy point from a cup base. It's also rebounding well from a test of its 10-week line. But the recent heightened volatility stands in stark contrast to several months of aggressive